jackson-module-kotlin: @JsonProperty is ignored on data class properties with names starting with "is"

Hi,

I’ve got a data class with a boolean property called isPublic. This property needs to be called exactly like that in JSON. However, since the property name starts with is, the prefix is stripped from the name. Adding @JsonProperty("isPublic") does not work either:

class JacksonTest {

    @Test
    fun serializeTest(){
        val objectMapper = ObjectMapper()
        objectMapper.registerKotlinModule()

        val instance = MyClass(true)
        val json = objectMapper.writeValueAsString(instance)

        assertEquals("""{"isPublic":true}""", json.replace("""\s+""".toRegex(), ""))
    }

    data class MyClass(
        @JsonProperty("isPublic")
        val isPublic: Boolean
    )

}

… fails with an assertion error:

java.lang.AssertionError: Expected <{"isPublic":true}>, actual <{"public":true}>.

It doesn’t matter what you pass into the @JsonProperty annotation, in the JSON output the field is always (!!) called public.

About this issue

Original URL
State: closed
Created 5 years ago
Reactions: 7
Comments: 17 (4 by maintainers)

Links to this issue

java - Usage of Jackson @JsonProperty annotation for kotlin data classes - Stack Overflow

Commits related to this issue

Fixing is* prefix issue. Refer: 1. https://github.com/FasterXML/jackson-module-kotlin/issues/237#issuecomment-775519984 2. https://github.com/FasterXML/jackson-module-kotlin/issues/453#issuecomment-8... — committed to 5AbhishekSaxena/print-ms by 5AbhishekSaxena 2 years ago
Update release note wrt #237 — committed to k163377/jackson-module-kotlin by k163377 a year ago
Update release note wrt #237 — committed to FasterXML/jackson-module-kotlin by k163377 a year ago

Most upvoted comments

Same! Any solution? I thought that I made mistake somewhere in the configuration.

My code:

data class PlayerResponse(
  @JsonProperty("abc")
  val accountId: Long,

  @JsonProperty("def")
  val isAdmin: Boolean,

  @JsonProperty("ghi")
  val isConnected: Boolean
)

val mapper = jacksonObjectMapper().apply {
    registerModule(ParameterNamesModule())
    registerModule(Jdk8Module())
    registerModule(JavaTimeModule())
  }

  val json = mapper.writeValueAsString(PlayerResponse(1, true, true))

Response:

{"abc":1,"admin":true,"connected":true}

Use @get:JsonProperty(“abc”) and @param:JsonProperty(“abc”) annotation on Boolean field instead of @JsonProperty(“abc”)

+19

MaksimRT on Oct 18, 2019

Changing @JsonProperty(“fieldname”) to @field:JsonProperty(“fieldname”) resolves the issue for data classes’ “is” (Boolean) properties.

mkheck on Feb 8, 2021

The only workaround I’ve found is to rename the field in your (data) class, and then expose it with @JsonProperty like so:

data class MyDTO(

    @JsonProperty("isConnected")
    val connected: Boolean   // do NOT call this "isConnected"!

)

That worked for me, YMMV.

MartinHaeusler on Oct 18, 2019

Thanks @MaksimRT Just adding @get:JsonProperty(“abc”) worked for me. I did not add @param:JsonProperty(“abc”) and it still worked. Is there any specific reason why you added @param:JsonProperty(“abc”) as well?

Hi, you are welcome)

What version of the library do you use?)

MaksimRT on Aug 6, 2020

Same! Any solution? I thought that I made mistake somewhere in the configuration.

My code:

data class PlayerResponse(
  @JsonProperty("abc")
  val accountId: Long,

  @JsonProperty("def")
  val isAdmin: Boolean,

  @JsonProperty("ghi")
  val isConnected: Boolean
)

val mapper = jacksonObjectMapper().apply {
    registerModule(ParameterNamesModule())
    registerModule(Jdk8Module())
    registerModule(JavaTimeModule())
  }

  val json = mapper.writeValueAsString(PlayerResponse(1, true, true))

Response:

{"abc":1,"admin":true,"connected":true}

rafalschmidt97 on Oct 18, 2019